The effect of the broad-line region with geometrical structures on gamma-ray absorption in blazars

TL;DR

This paper investigates how the geometrical structure of the broad-line region in blazars influences gamma-ray absorption, revealing that certain geometries allow gamma-rays to escape more easily.

Contribution

It introduces a model analyzing the impact of BLR geometry on gamma-ray transparency, highlighting the significance of geometrical structure in gamma-ray absorption.

Findings

Gamma-ray optical depth varies with BLR geometry.

Flat BLR geometries permit gamma-ray escape from inside the cavity.

Gamma-ray transparency is highly dependent on the BLR's shape.

Abstract

The broad-line region (BLR) is an important component of blazars, especially for the flat spectrum radio quasars (FSRQs). The soft photons arising from the BLR will substantially affect the transparency of the gamma-ray photons produced in the relativistic jet. In the paper, we study the effect of the geometrical structure of the BLR on the absorption of gamma-rays. We find that the gamma-ray optical depth strongly depends on the geometrical structure of the BLR. For a "flat" geometry of the BLR, the gamma-ray photons with specified energies could escape transparently even their emission region locates inside the cavity of the BLR.